On Fri, Mar 26, 2021 at 11:07:58AM +1100, Alistair Popple wrote:
> Remove multiple similar inline functions for dealing with different
> types of special swap entries.
>
> Both migration and device private swap entries use the swap offset to
> store a pfn. Instead of multiple inline functions to obtain a struct
> page for each swap entry type use a common function
> pfn_swap_entry_to_page(). Also open-code the various entry_to_pfn()
> functions as this results is shorter code that is easier to understand.
>
> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
> Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
>
> ---
>
> v7:
> * Reworded commit message to include pfn_swap_entry_to_page()
> * Added Christoph's Reviewed-by
>
> v6:
> * Removed redundant compound_page() call from inside PageLocked()
> * Fixed a minor build issue for s390 reported by kernel test bot
>
> v4:
> * Added pfn_swap_entry_to_page()
> * Reinstated check that migration entries point to locked pages
> * Removed #define swapcache_prepare which isn't needed for CONFIG_SWAP=0
> builds
> ---
> arch/s390/mm/pgtable.c | 2 +-
> fs/proc/task_mmu.c | 23 +++++---------
> include/linux/swap.h | 4 +--
> include/linux/swapops.h | 69 ++++++++++++++---------------------------
> mm/hmm.c | 5 ++-
> mm/huge_memory.c | 4 +--
> mm/memcontrol.c | 2 +-
> mm/memory.c | 10 +++---
> mm/migrate.c | 6 ++--
> mm/page_vma_mapped.c | 6 ++--
> 10 files changed, 50 insertions(+), 81 deletions(-)
Looks good
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 943cb2ba4442..3b2dda71d0ed 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -214,7 +214,7 @@ static inline bool hmm_is_device_private_entry(struct hmm_range *range,
> swp_entry_t entry)
> {
> return is_device_private_entry(entry) &&
> - device_private_entry_to_page(entry)->pgmap->owner ==
> + pfn_swap_entry_to_page(entry)->pgmap->owner ==
> range->dev_private_owner;
> }
>
> @@ -257,8 +257,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
> cpu_flags = HMM_PFN_VALID;
> if (is_write_device_private_entry(entry))
> cpu_flags |= HMM_PFN_WRITE;
> - *hmm_pfn = device_private_entry_to_pfn(entry) |
> - cpu_flags;
> + *hmm_pfn = swp_offset(entry) | cpu_flags;
Though swp_offset() seems poor here
Something like this seems nicer, maybe as an additional patch in this
series?
diff --git a/mm/hmm.c b/mm/hmm.c
index 943cb2ba444232..c06cbc4e3981b7 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -210,14 +210,6 @@ int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-static inline bool hmm_is_device_private_entry(struct hmm_range *range,
- swp_entry_t entry)
-{
- return is_device_private_entry(entry) &&
- device_private_entry_to_page(entry)->pgmap->owner ==
- range->dev_private_owner;
-}
-
static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
pte_t pte)
{
@@ -226,6 +218,32 @@ static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
return pte_write(pte) ? (HMM_PFN_VALID | HMM_PFN_WRITE) : HMM_PFN_VALID;
}
+static bool hmm_pte_handle_device_private(struct hmm_range *range, pte_t pte,
+ unsigned long *hmm_pfn)
+{
+ swp_entry_t entry = pte_to_swp_entry(pte);
+ struct page *device_page;
+ unsigned long cpu_flags;
+
+ if (is_device_private_entry(entry))
+ return false;
+
+ /*
+ * If the device private page matches the device the caller understands
+ * then return the private pfn directly. The caller must know what to do
+ * with it.
+ */
+ device_page = pfn_swap_entry_to_page(entry);
+ if (device_page->pgmap->owner != range->dev_private_owner)
+ return false;
+
+ cpu_flags = HMM_PFN_VALID;
+ if (is_write_device_private_entry(entry))
+ cpu_flags |= HMM_PFN_WRITE;
+ *hmm_pfn = page_to_pfn(device_page) | cpu_flags;
+ return true;
+}
+
static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
unsigned long end, pmd_t *pmdp, pte_t *ptep,
unsigned long *hmm_pfn)
@@ -247,20 +265,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
}
if (!pte_present(pte)) {
- swp_entry_t entry = pte_to_swp_entry(pte);
-
- /*
- * Never fault in device private pages, but just report
- * the PFN even if not present.
- */
- if (hmm_is_device_private_entry(range, entry)) {
- cpu_flags = HMM_PFN_VALID;
- if (is_write_device_private_entry(entry))
- cpu_flags |= HMM_PFN_WRITE;
- *hmm_pfn = device_private_entry_to_pfn(entry) |
- cpu_flags;
+ if (hmm_pte_handle_device_private(range, pte, hmm_pfn))
return 0;
- }
required_fault =
hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0);
Jason
